U-shaped cradle for circuit breaker



Nov. 3, 1964 E. R. WORTMANN 3,155,802

U-SHAPED CRADLE FOR CIRCUIT BREAKER Filed May 9. 1961 6 Sheets-Sheet 1IN VEN TOR. ae/v'sr f WO PT MW Nov. 3, 1964 I E. R. WORTMANN 3,155,302

U-SHAPED CRADLE FOR CIRCUIT BREAKER Filed May 9, 1961 6 Sheets-Sheet 2CDCD' n l BY INVENTOR. h m 5v A. IK/OEr/ M/M Nov. 3, 1964 E. R. WORTMANN3,155,302

U-SHAPED CRADLE FOR CIRCUIT BREAKER Filed May 9, 1961 6 Sheets-Sheet 5 IN V EN TOR. 501 552" 1?. zwer/v/i/v/v Nov. 3, 1964 E. R. WORTMANNU-SHAPED CRADLE FOR CIRCUIT BREAKER W I I M 6 Sheets-Sheet 4 l "1 n "E;

Filed May 9, 1961 Nov. 3, 1964 E. R. WORTMANN U-SHAPED CRADLE FORCIRCUIT BREAKER 6 Sheets-Sheet 5 Filed May 9. 1961 Nov. 3, 1964 E. R.WORTMANN 3,155,802

U-SHAPED CRADLE FOR CIRCUIT BREAKER Filed May 9, 1961 6 Sheets-Sheet 6INVENTOR. 4 ERA 5 7 WOffMflA W Affa/ewzw' United States Patent $355,362FLT-SHAPED ClEADlLE BUR ClllQlJlli Ernest ll. Wortmann, Dreael il'ill,Pa, assignor to l-='ll=ll Circuit Breaker tlompan Philadelphia, Pin, acorp-w ration of Pennsylvania Filed May 9, 1961, Ser. No. 5,312 ll@lalms. (ill. fwd- 153) This invention relates to multi-phase moldedcase circuit breakers in general and more particularly to a novelconstruction for the contact operating mechanism thereof, including aU-shaped cradle the utilization of which achieves faster contact speedand enables greater contact separation for a given overall case size.

In multi-phase molded case circuit breakers it is customary to utilize asingle contact operating mec ianism for all phases. Typically, a circuitbreaker of this type is a three-phase unit in which the current carryingpaths through the phases are identical and parallel to each other withthe single operating mechanism positioned the center phase.

The contact operating mechanism usually comprises a latchable cradlemechanism for supporting a toggle linkage operatively connected to movethe movable contacts into and out of engagement with the stationarycontacts under the influence of the main operating springs. With thecradle unlatched the mechanisms cannot operate the toggle linkage so asto bring the contacts into engagement.

in previous designs the cradle was placed in the center plane of themechanism between the toggle linkages and the operating springs. Aslarger contact travel was required in order to obtain greater contactseparation, it became necessary to move the cradle pivot away from thearea of contact motion or else shape the movable contact arm in such amanner as to clear the cradle bushing when the contacts were disengaged.Either prior art arrangement required increased overall mechanism heightwhich is usually not available. It was thought that moving the cradlebushing would solve the problem. How ever, it was found that additionalclearance for the operating springs was required when the cradle bushingwas moved.

is a means of saving material and space circuit breaker designers havefor years been striving to achieve more compact constructions. For thereasons outlined above, a limiting factor appea ed to be the cradlebushing.

The instant invention overcomes the dirficulty of the prior art byproviding a latchable cradle constructed as a U-shaped member with thebushings therefor extending outwardly from the arms of the U. The togglelinkage and operating springs are placed between the arms of the U.Since the cradle bushing does not span the toggle linkage and springarea, the cradle bushing does not interfere with movement of the springor contact linkage, so that greater contact travel and increasedoperating forces are possible within smaller space limits than waspossible with prior art constructions.

Prior art constructions, in order to preserve symmetry,

required that an equal number of springs be positioned on each side ofthe cradle. Thus, at least two springs were required. With theutilization of a U-shapcd cradle, a single operating spring may beutilized, thereby reducing the number of parts and the number ofhandling operations required during assembly. Even when two springs areutilized they may be placed side by side in the center plane of themechanism so that overall width may be maintained at a minimum. in priorart constructions the springs were on opposite sides of the centerplane.

The circuit breaker construction to be hereinafter described includesmeans whereby contact travel is more rapid during an automatic trippingoperation than in contact travel of prior art devices. In prior artdevices, dur'ag the tripping operation the movable contact arm movedvery little during the initial large movement of the cradle until suchtime as the knee of the toggle was moved over center. By this time theoperating springs had eX pended most of their energy, so that movementof the contact arm thereafter for most of its travel was at a relativelyslow speed.

In the device to be hereinafter described, the knee of the toggle restsagainst the cradle when the circuit breaker is closed. Upon automatictripping the cradle and toggle move as a unit for a very short distance.Thereafter, a stationary surface is engaged by a rounded surface of oneof the toggle links, driving the knee of the toggle over center verysoon after movement of the cradle is initiated and while the operatingsprings are still heavily loaded. Thus, from this point on, movement ofthe contact arm is very rapid, resulting in improved interruption.

The construction to be hereinafter described is such that with thecontacts fully separated after an automatic tripping operation, therounded surface of the toggle, previously mentioned, is positionedextremely close to a stationary surface. If the movable contact tends torebound, the rounded surface reengages the stationary surface, therebylimiting the rebound of the contact arm to a very short travel.Additional travel is strongly resisted by the operating spring. Inaddition, oscillations are very slight since the operating spring isvery lightly loaded until the surfaces engage on rebound.

In prior art circuit breakers, as the contacts are brought intoengagement the toggle linkage, as it is brought over center, has themovement thereof abruptly arrested by engagement with a surfacepositioned normal to its direction or" toggle travel. This places agreat strain on the connecting pins of the toggle and cradle. in thedevice of this invention, upon circuit breaker closing, the knee of thetoggle engages a surface of the cradle positioned at an incline withrespect to the knee direction of travel. The sloping surface permitsovertravel with the contact pressure spring absorbing excess energy.

Accordingly, a primary object of this invention is to provide a novelcontact operating mechanism for a circuit breaker.

Another object is to provide a contact operating mechanism in which thecradle is a U-shaped member with the toggle linkage and operatingsprings placed between the arms of the U.

Still another object is to provide a novel circuit breaker mechanism forobtaining a large contact motion together with a high closing force.

A still further object of this invention is to provide a contactoperating mechanism with novel means for reducing wear of the cradle andtoggle linkage pins.

Another object is to provide an operating mechanism for a mult-i-phasecircuit breaker which requires only a single operating spring.

These as well as other objects of this invention shall become readilyapparent after reading the following escription of the accompanyingdrawings in which:

FIGURE 1 is a perspective of a circuit breaker constructed in accordancewith the teachings of the instant invention. The cover of the circuitbreaker is removed to reveal the internal mechanism thereof.

Fl -UB5 2 is a plan view of the circuit breaker in FIGURE 1 with thecover removed.

FEGURE 3 is a cross-section taken through the center phase of thecircuit breaker through line 3-3 of FIG- URE 2 looking in the directionof arrows 3-3.

FXGURES 47 are side elevations of the contact operating mechanism withcertain elements partially cut away. in PlGURE 4 the circuit breaker isin the closed position. in FIGURE 5 the circuit breaker, after having'Operating member 45 straddles been in a closed position, is tripped andthe upper toggle linkage has just engaged a stationary surface of theframe, which will rapidly force the knee of the toggle over center. openposition. In FIGURE 7 the mechanism is in the manual open position.

FIGURE 8 is an exploded view of the contact operating mechanism.

Now referring to the figures; circuit breaker It? is provided with amolded insulating housing comprising base 11 and removable cover 12joined along line I3. Circuit breaker It is a three-phase unit, so thatbase ill is divided into three parallel compartments by partitions Id,15. Each of the parallel compartments houses the current carryingmembers for the respective phases.

Since each phase is comprised of identical-current carrying members,only the current carrying parts of the center phase will be described.These current carrying parts comprise load terminal connecter 16, loadterminal 17, the looped extension 18 thereof extending throughinstantaneous trip magnet 19, through a portion 20 of terminal 17 havinga reduced cross-section so as to serve as an indirect heater for bimetaltime delay tripping element 21. The current path continues throughconductor 22, flexible braid 23, movable contact arm 24, and movablecontact 25 to stationary contact 26, which is mounted upon line terminalstrap 27, having tulip line terminal connecter 28 mounted thereto byscrew means 29.

The movable contacts 25 of all three phases are operated simultaneouslyinto and out of engagement with their respective stationary contacts 26by means of a single operating mechanism. 3% which is positioned in thecenter compartment. Each of the movable contact arms 24 is pivotallymounted at 31 to its individual U-shaped holder 32 between the armsthereof. Each holder 32 is provided with a portion 33 which defines arectangular opening having insulating tie rod 3d disposed therein. Tierod 34 extends through all three housing compartments so that thecontact arm holders 32 of all three phases are mounted thereto. Theouter phases are each provided with angle brackets 35 which providesupport for bearing pins 3b to which holders 32 are pivotally mounted.It is clearly seen that movement of tie rod 34 brings about thesimultaneous movement of all three contact arms 242-.

Leaf spring 37, fixedly mounted to holder 32 by rivet 3%, acts uponadjusting screw 39 to urge contact arm 24 in a counterclockwisedirection with respect to FIG- URE 3 toward engagement withholdersurface ill. As clearly shown in FIGURE 3, when contacts 25, 26 are inengagement, contact arm 24 is spaced from holder surface 4b. In theouter two phases, screw means 41 secures load terminal member conductor22 and bracket 35 to base lll, while in the center phase screw means 41secures load terminal strap 17, conductor 22 and mechanism frame 42 tobase llll.

Frame 42 is a somewhat U-shaped member having pins extending outwardlyfrom the arms thereof. frame 42 with pins 44 being disposed within theopen ended slots 43 at the lower end (with respect to FIGURE 1) ofoperating member 45. Manual operating handle 49 is mounted at the upperend of member 45 and includes a portion extending externally of housingas, I2 through aperture in cover 12. Spring 51, interposed betweenmember 45 and handle 4.9 biases a portion ofhandle 49 against the innersurface of cover 12.

In FIGURE 6 the mechanism is in the tripped Intermediate latch member-56 is pivotally mounted Bar 55 is an insulating member extending acrossall three base compartments being pivotally mounted at the ends thereofto uprights 56. Tension spring 57 biases bar counterclockwise tolatching position which is established through its engagement withadjusting screw threadably mounted to one of the uprights 56.

Operating mechanism also includes cradle dd, a toggle linkage comprisinglinks 62, es, and operating spring means 64, 65. As best seen in FIGURE2, cradle 6-3 is a generally U-shaped member whose web fill faces theload end of circuit breaker it when cradle 6t) is in latched position asin FIGURES 4 and 7. Cradle 69 is maintained in this position through theengagement of latch plate so, mounted to web er, with the web 67 ofintermediate latch member 4-6, whose extension 53 is in engagement withlatch plate 54, carried by tripper bar 55. Cradle titl is biased to itstripped position of FIGURE 6 by spring means 64, 65, as will becomeevident as this description proceeds.

Common tripper bar 55 is rotatable in a clockwise direction upon theoccurrence of predetermined circuit conditions to release thecooperative engagement of members 53, 54 and 66, e7. That is, upon theoccurrence of a persisting fault the free end of bimetal 21 deflects tothe right with adjusting screw 68 engaging tripper bar extension 69.Upon the occurrence of a severe overload, armature 70 will be attractedby magnet 19 with adjusting screw '71 moving to the left to engagetripper bar extension '72.

Pins 77 extending outwardly from the arms of cradle 6t pivotally mountcradle so to frame 42; Toggle linkage 62, 63 as well as spring means 64,65 are mounted between the arms of cradle 60. It is to be noted thateach of the toggle links 62, 63 are split members.

Lower toggle link as is connected at one end to movable contact arm 24-at pin 31 while the other end is connected to pin 73 which forms theknee of toggle linkage 62, 63. Upper toggle link 62 is connected at oneend to pin 73 and at the other end is pivotally connected at '74 tocradle so. The upper ends of springs 64, 65 are secured to operatingmember 45 while the lower ends of springs 64, 65 are secured to plate'75 which is pivotally mounted to pin '73. Collars 76 position links 62,63 axially on pin 73.

Springs 64, 65 are tension members so it is readily seen that they biascradle 60 counterclockwise about pins 77, bias operating member 45against pins 4-3, and bias contacts 25, 26 both into and out ofengagement depending upon the position of toggle knee 73.

Circuit breaker Ill is operated manually between the 0n (FIGURE 4) andOff (FIGURE 7) positions by means of handle 49. With circuit breakerlltl closed movement of handle 49 to the right with respect to FIG- URE4 moves the upper end of springs 64, as to the right. .At such time asthe force of springs 64, 65 acts along the line positioned to the rightof the line joining knee '73 and pivot 74, knee 73 will be drawn overcenter to the rightand contacts 25, 26 will be operated to thedisengaged position of FIGURE 7. It is to be noted that contact arm 24has passed through a line extending between the cradle bushings formedby spaced pins 77 so that a large contact separation is obtained Theopen position of contact arm 24 is established by the engagement ofholder projections 78 with cradle on near its pivot '77. e

In operating contacts 25,26 into engagement toggle knee 73 moves rapidlyto the left with respect to FIG- URE 7. ts movement must be arrested ina very short time interval. This is accomplished by having the ends ofknee pin 73 engage cradle surface 85. It is to be noted that surface ispositioned at a substantial incline, approximately 45, with respect tothe direction of travel of pin 73 just prior to its stoppage. i Inclinedsurface 85 causes a downward component of force to be exerted on contactarm holder 32; with this component of force being absorbed by contactarm biasing spring 37; J

areasoa As circuit breaker 1d operates from the On position of FIGURE 4to the tripped position of FIGURE 6,

cradle 66 and toggle links 62, 63 move substantially as a unit clockwiseabout bushing '77 for a short distance during which the contacts remainengaged. Thereafter, as seen in FIGURE 5, the rounded cam surface 8t?engages the frame inward extension 81.

Cradle 6% continues counterclockwise carrying the pivot 74 for togglelink 62 to the left forcing toggle knee 73 rapidly to the right. Thus,for a relatively short cradle movement toggle knee 73 moves over centerand an almost fully loaded spring means 64, 65 is then free to bringabout rapid contact separation.

Not only does the engagement of surfaces 80, 81 serve to kick toggleknee 73 over center but it also serves as an anti-rebound means. Thatis, when circuit breaker 16 trips open, contact arm 24 tends to reboundclosed from the tripped position of FIGURE 6. In doing so toggle 62, 63must be extended soon bringing earn surface Eli) into engagement withframe 42 at 31. Continued movement of contact arm 24 toward closedposition is strongly resisted by springs 64. 65 which in this positionrequire strong forces for loading thereof.

Cradle 69 is returned to latched position through the engagement ofoperating member projection 83 which engages cradle 64! at 34.

Although there has been described preferred embodiments of thisinvention, many variations and modifications will now be evident tothose skilled in the art and, therefore, the scope of this invention isto be limited not by the specific disclosure herein detailed, but onlyby the appended claims.

I claim:

1. In a circuit breaker, a pair of cooperating contacts and a mechanismfor operating said contacts into and out of engagement; said mechanismcomprising a latchable cradle, a movable contact arm carrying one ofsaid cooperating contacts, first means connecting said cradle and saidcontact arm in a manner such that said contacts cannot be operated intoengagement unless said cradle is in a latched position, an operatingspring means urging said cradle to a tripped position; said cradlecomprising a U-shaped member; a pivotal mounting for said cradle, saidmounting comprising individual pin means for each arm of the cradle,said pin means being axially aligned and spaced from each other, each ofsaid pin means extending outboard of its respective arm; said contactarm movable in the region intermediate said arms and through the axis ofsaid pin means when operating into and out of engagement.

2. In a circuit breaker, a pair of cooperating contacts and a mechanismfor operatin said contacts into and out of engagement; said mechanismcomprising a latchable cradle, a movable contact arm carrying one ofsaid cooperating contacts, first means connecting said cradle and saidcontact arm in a manner such that said contacts cannot be operated intoengagement unless said cradle is in a latched position, an operatingspring means urging said cradle to a tripped position; said cradlecomprising a U-shaped member; a pivotal mounting for said cradle, saidmounting comprising individual pin means for each arm of the cradle,said pin means being axially aligned and spaced from each other, each ofsaid pin means extending outboard of its respective arm; said contactarm and said first means being positioned between the arms of thecradle; said contact arm movable in the region intermediate said arms,and through the axis of said pin means, when operating into and out ofengagement.

3. In a circuit breaker, a pair of cooperating contacts and a mechanismfor operating said contacts into and out of engagement; said mechanismcomprising a latchable cradle, a movable contact arm carrying one ofsaid cooperating contacts, first means connecting said cradle and saidcontact arm in a manner such that said contacts cannot be operatedinto-engagement unless said cradle is in a latched position, anoperating spring means urging said cradle to a tripped position; saidcradle comprising a U-shaped member pivotally mounted on pins extendingoutwardly of the U-arms; said contact arm and said first means beingpositioned between the U-arms; said first means comprising a togglelinkage with one end connected to said cradle and the other endconnected to said contact arm; said contact arm movable in the regionintermediate said arms and through the axis of said pin means whenoperating into and out of engagement.

4. In a circuit breaker, a pair of cooperating contacts and a mechanismfor operating said contacts into and out of engagement; said mechanismcomprising a latchable cradle, a movable contact arm carrying one ofsaid cooperating contacts, first means connecting said cradle and saidcontact arm in a manner such that said contacts cannot be operated intoengagement unless said cradle is in a latched position, an operatingspring means urging said cradle to a tripped position; said cradlecomprising a U-shaped member pivotally mounted on pins extendingoutwardly of the U-arms; said contact arm and said first means beingpositioned between the U-arms; said first means comprising a togglelinkage with one end connected to said cradle and the other endconnected to said contact arm; said spring means comprising a tensioningmember secured at one end to the toggle knee and positioned between theU-arms.

5. In a circuit breaker, a pair of cooperating contacts and a mechanismfor operating said contacts into and out of engagement; said mechanismcomprising a latchable cradle, a movable contact arm carrying one ofsaid cooperating contacts, first means connecting said cradle and saidcontact arm in a manner such that said contacts cannot be operated intoengagement unless said cradle is in a latched position, an operatingspring means urging said cradle to a tripped position; said cradlecomprising a U-shaped member pivotally mounted on pins extendingoutwardly of the U-arms; said contact arm being mounted to a stationarypivot and having a portion movable through a line extending between saidpins as said contacts are operated into and out of engagement.

6. in a circuit breaker, a pair of cooperating contacts and a mechanismfor operating said contacts into and out of engagement; said mechanismcomprising a latchable cradle, a movable contact arm carrying one ofsaid cooperating contacts, first means connecting said cradle and saidcontact arm in a manner such that said contacts cannot be operated intoengagement unless said cradle is in a latched position, an operatingspring means urging said cradle to a tripped position; said cradlecomprising a U-shaped member pivotally mounted on pins extendingoutwardly of the U-arms; said contact arm and said first means beingpositioned between the U-arms; said first means comprising a togglelinkage with one end connected to said cradle and the other endconnected to said contact arm; said spring means comprising a tensioningmember secured at one end to the toggle knee and positioned between theU-arms; said spring means comprising a first and a second coiled memberpositioned in a plane extending parallel to the plane of movement ofsaid cradle and acting generally in the same direction.

7. In a circuit breaker, a pair of cooperating contacts and a mechanismfor operating said contacts into and out of engagement; said mechanismcomprising a latchable cradle, a movable contact arm carrying one ofsaid cooperating contacts, first rneans connecting said cradle and saidcontact arm in a manner such that said contacts cannot be operated intoengagement unless said cradle is in a latched position, an operatingspring means urging said cradle to a tripped position; said cradlecomprising a U-shaped member pivotally mounted on pins extendingoutwardly of the U-urms; said contact arm and said first meanscomprising a toggle linkage with one end connected to said cradle andthe other end connected to said "i 9 contact arm; said spring meanscomprising a tensioning member secured at one end to the toggle knee andpositioned between the U-arms; said spring means comprising a first anda second coiled member positioned in a plane extending parallel to theplane of movement of said cradle and acting generally in the samedirection; said coiled members each being centered between said U-arms.

8. In a circuit breaker, a pair or" cooperating contacts and a mechanismfor operating said contacts into and out of engagement; said mechanismcomprising a latchable cradle, a movable contact arm carrying one ofsaid cooperating contacts, first means connecting said cradle and saidcontact arm in a manner such that said contacts cannot be operated intoengagement unless said cradle is in a latched position; an operatingspring means urging said cradle to a tripped position; said cradle beingpivotally mounted at stationary bushing means and including a saeoafirst and a second arm; said contact arm and said first means beingpositioned between said arms.

9. The circuit breaker as set forth in claim 8 in which the spring meanscomprises a tensioning member positioned between said arms.

10. "i" he circuit breaker as set forth in claim 9 in which the bushingmeans is comprised of pins extending outboard of said first and saidsecond arms.

11. The circuit breaker as set forth in claim 10 in which the contactarm is mounted to a stationary pivot and includes a portion movablethrough a line extending between said pins as said contacts are operatedinto and out of engagement.

References Cited in the file of this patent Urnrnn STATES PATIENTS2,829,219 Christensen Apr. 1, 1958

1. IN A CIRCUIT BREAKER, A PAIR OF COOPERATING CONTACTS AND A MECHANISMFOR OPERATING SAID CONTACTS INTO AND OUT OF ENGAGEMENT; SAID MECHANISMCOMPRISING A LATCHABLE CRADLE, A MOVABLE CONTACT ARM CARRYING ONE OFSAID COOPERATING CONTACTS, FIRST MEANS CONNECTING SAID CRADLE AND SAIDCONTACT ARM IN A MANNER SUCH THAT SAID CONTACTS CANNOT BE OPERATED INTOENGAGEMENT UNLESS SAID CRADLE IS IN A LATCHED POSITION, AN OPERATINGSPRING MEANS URGING SAID CRADLE TO A TRIPPED POSITION; SAID CRADLECOMPRISING A U-SHAPED MEMBER; A PIVOTAL MOUNTING FOR SAID CRADLE, SAIDMOUNTING COMPRISING INDIVIDUAL PIN MEANS FOR EACH ARM OF THE CRADLE,SAID PIN MEANS BEING AXIALLY ALIGNED AND SPACED FROM EACH OTHER, EACH OFSAID PIN MEANS EXTENDING OUTBOARD OF ITS RESPECTIVE ARM; SAID CONTACTARM